The National Grid (WJEC GCSE Science (Double Award)): Revision Note

The National Grid

• The National Grid is the distribution system for electricity across the UK

  • The National Grid monitors power usage and responds to changing demand

    • Peak usage time is around 6 pm when people are cooking their evening meals

    • Usage is higher in the winter than the summer as people use more lighting and heating

• Electrical energy is transferred from power stations to consumers using the National Grid

• The National Grid consists of a system of cables and transformers linking power stations to consumers (houses, factories and buildings)

• Current flows through the network of cables transferring energy 

  • When current flows in a wire, there is heating in the wire due to resistance

  • Therefore, energy is dissipated to the surroundings, this energy is wasted

  • The greater the current, the less efficient the energy transfer

• The National Grid uses a low current to prevent this dissipation of energy in the cables

• It does this by increasing the voltage when the current enters the National Grid

Power = voltage × current

• This high-voltage transmission ensures the same power transfer with a smaller current

• High voltage is dangerous for use in homes, so the voltage is lowered before the current reaches consumers

• This stepping up and stepping down of the voltage is done by transformers

Use of Transformers

• Step-up transformers are used to increase the voltage from the power station to the transmission cables

• Step-down transformers are used to decrease the voltage, to a much lower value, from the transmission cables to the consumer

The National Grid

The National Grid is a system of cables and pylons that transfers energy from power stations to consumers